Circuit interrupter



2 Sheets-Sheet l E. E. ARNOLD CIRCUIT INTERRUPTER Filed Aug. 26, 1942Oct. 24, 1944.

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06L 24, ARNOLD CIRCUIT INTERRUPTER Filed Aug. 26, 1942 2 Sheets-Sheet 256 74V 76 74 a0 1 6.9 7 I 4 f4 19 1a 22 48 1 V "4- I 14 6 4 20 21 Z I 40yllllizlllll Ii! III 12 WITNESSES: INVENTOR EJ212172 ZZZ Arne/a.

Patented Oct. 24, 1944 I UNITED STATES- PATENT OFFICE CIRCUITINTERRUPTER Edwin E. Arnold, Pittsburgh, Pa., assignor to WestinghouseElectric & Manufacturing Company, East Pittsburgh, Pa., a corporation ofPennsylvania Application August 26, 1942, Serial No. 456,195

24 Claims.

This invention relates to circuit interrupters,

in general, and, more particularly, to interrupter ing a snap-actingbimetal element for actuating the breaker contacts.

Another object of this invention is to provide in a circuit breaker ofthe type described, a novel arrangement of a snap-acting bimetalcontactactuating element with supporting and actuating means therefor.

Another object of this invention is to provide novel double-break meansfor a current-carrying contact-actuating member.

Another object of this invention is to provide in a circuit breaker ofthe type described, novel means for obtaining a double break in thecircuit upon a circuit interrupting operation.

Still another object of this invention is to pro vide a novel circuitbreaker which is small in size, while capable of emciently interruptingrelatively high currents.

' These and other objects of this invention will become more apparentupon consideration of the following detailed description of preferredembodiments thereof when taken in connection with the attached drawings,in which:

Figure 1 is a longitudinal sectional view of a circuit breakerconstructedin accordance with this invention with certain parts of thebimetal broken away and shown in section;

Fig. 2 is a top plan view of the circuit breaker shown in Fig. 1 withthe cover for the breaker casing removed;

Fig. 3 is a transverse section through the circuit breaker shown in Fig.1 taken substantially on the line III-III thereof; with the breakershown in open position,

Fig. 4 is a longitudinal section like Fig. 1 of a slightly modified formof circuit breaker;

Fig.5 is a transverse section taken substantially on the line V-Vthrough the breaker shown in Fig. 4; and

Fig. 6 is a longitudinal sectional view like Figs. 1 and 4 of a stillfurther modified form of circuit breaker.

Circuit breakers constructed in accordance with this invention arepreferably mounted within a casing of insulating material, such as amolded insulating material, and such a casing may comprise a bottom wall2, end walls 4, side walls 8,

and an open top. The top of the casing may be closed by a removablecover 8 suitably securedin position, for example,'as by screws 9.Breaker terminals III and I2 extend through the bottom wall 2 oi! thebreaker casing, and have their outer ends threaded for the reception ofnuts to secure line conductors thereto. The inner ends of terminals I0and I2 are preferably enlarged, as shown, for a purpose to behereinafter described.

ment I4 secured thereto as by brazing, welding,

- or the like, and the contact element may be of 15 shaped support I6 isprovided within a dove-tail groove in the inner end of terminal I2 for apurpose to be described.

A substantially rectangular-shaped bimetal element I8 is provided, andthis is formed with a pair of spaced longitudinally extending slotsproviding side legs 20, and a substantially centrally located leg 22,all extending longitudinally of bimetal element I8. The element I8 isformed of two metallic laminations in a well known manner, such aslaminations I9 and 2|, of materials having, respectively, relatively lowand high coeillcients of thermal expansion. Thus, the lamination I9 maybe of a material, such as iron, which has a lower coefficient of thermalexpansion than brass, which may comprise the material of lamination 2I.The two metallic laminations are secured together in any desiredrelation, such, for example, as by welding. It will be noted that theside legs 280i bimetal element I8 35 are provided with bent portions forshortenin side legs 20. This will place central leg 22 undercompression, and cause it to assume a longitudinally bowed position, asshown, for example, in Fig. 1. The bimetal element I8 when heated, whilein the position shown in Fig. 1, will bend towards a position in whichit is concave in an upward direction. However, this bending is opposedby central leg 22. Accordingly, a relatively great force is required tobend the bimetal upwardly until side legs 28 pass overcenter withrespect to central leg 22, whereupon the central leg 22 reverses itscurvature and becomes bowed downwardly and assists further bending ofbimetal element I8 in the upward direction. This assistance due toreversal of the curvature of central leg 22 adds to the sudden releaseof the relatively great force tending to bend the bimetal elementupwardly from the position shown in Fig. 1, resulting in movement of thebimtal with a quick or snap-action.

The inner end of terminal III has a contact eler The central leg 22 ofbimetal element II is provided with a centrally located aperture forreceiving a shouldered supporting stud 28 having the end thereof rivetedover bimetal element It to rotatably secure the bimetal element to thestud. Stud 26 is adapted to be threadedly received within a threadedbushing 28 secured in an aperture in a supporting plate 30. As viewed inFig. 2, it will be observed that supporting plate 30 is provided with apair of spaced ears 32 on each side thereof in opposed relation. Theears 32 are for the purpose of securing supporting plate 30 within thecircuit breaker casing, and to this end, the opposite side walls 8 ofthe casing are provided at the inner surfaces thereof with opposedparallel grooves 34 extending from the top of the casing downwardlytoward bottom wall 2, and these grooves intersect with grooves 36extending at right angles thereto. Accordingly, it will be observed thatsupporting plate 30 may be removed from the casing when cover 8 isremoved by shifting plate 30 to the right, as viewed in Fig. 1, untilears 32 come into alignment with grooves 34, whereupon the supportingplate may be lifted out of the casing. Obviously the plate may beinserted 'in the casing by the reversal of the above procedure.

Bimetal element l8 has secured to one en thereof an extension plate 38,for example, as by rivets 39. The extension plate 38 is provided at theunderside thereof with a transversely extending groove for receiving theupper edge of wedge-shaped support member 16. Extension 38 may bemaintained in the position shown in Fig. 1 wherein the upper edgeLWedge-shaDed element is is maintained within a transverse groove in theextension, by a threaded retaining pin All extending through oppositeside walls 8 of the casing to be threadedly engaged in one side walljust above the extension 38 to prevent lateral movement thereof, andprovide a loose or pivotal mounting for the outer end of the extension.

An operating handle 42 is secured to the end of bimetal element I!adjacent extension plate 38 as by one of the rivets l9, and the handleextends upwardly through an aperture 44 provided in cover 8 for manualmanipulation thereof from the exterior of the casing.- The free end ofbimetal element i8 is provided with an opening 48 cut into the endthereof for receiving a bridging contact 50 which is adapted to providea double break in the circuit when the bimetal element is actuated toopen circuit position. Bridging contact 50 has clearance with opening 48and is secured to one end of a leaf spring 52, the other end of which issecured between bimetal element l8, and the shoulder on supporting stud26, so as to be fixed with respect to the central portion of central leg22 of bimetal element II. Leaf spring 52 is preferably of spring steelwhich has a higher electrical resistance than the material comprisingbimetal element l8, or, if desired, leaf spring 52 may be formed ofinsulating material. A contact bridge 54 is substantially U-shaped inform with the legs thereof secured at opposite sides of bimetal elementl8 and with the base thereof extending across the free end of thebimetal element to form a bridge directly over bridging contact 50. Anadjustable stop screw 56 is threadedly mounted in an aperture providedin supporting plate 30, to limit upward movement of the free endofbimetal element I8.

The circuit breaker is illustrated in the closed circuit position inFig. 1, wherein side legs 20 of ter of central leg 22 so that the freeend of the bimetal element is biased downwardly and bridging contact 50engages contact element It on terminal It at one end,and is engaged bycontact bridge 54 at its other end. The circuit through the breaker thenextends from one terminal ll through bridging contact 50, contact bridge54, bimetal element I8, extension plate 38, wedgeshaped member l5 toterminal l2. In case it is desired to manually operate the breaker toopen circuit position, operating handle 42 is moved to the right, asviewed in Fig. 1, thereby raising side legs 20 of the bimetal elementpast the supporting point of central leg 22 on stud 25, whereupon thebimetal element operates with a snap action, as previously described, tomove the free end thereof upwardly. Leaf spring 52 normally maintainsbridging contact 50 in the position shown in Fig. 3 of the drawings,wherein it is spaced below contact bridge 54. Accordingly, when the freeend of bimetal element ll moves upwardly, leaf spring 52 maintainsbridging contact 50 in engagement with contact element H, while contactbridge 54 separates from the top of bridging contact 50 until leafspring 52 engages'the outer end of bimetal element ll, whereupon thebridging contact 50 is separated from contact element l4. It will beobserved that in the open circuit position, bridging contact 50 is notonly spaced from contact element H, but is also spaced from contactbridge 54 to thereby provide series gaps in circuit, since leaf spring52 is of high resistance material or insulating material. A furtheradvantage of this contact construction resides in the fact that duringinitial opening movement of the contacts, when contact bridge 55separates from bridging contact 50, but before bridging contact 50separates from contact element I 4, a high resistance (resilient element52) is inserted in the circuit before any gap is actually provided.This, of course, applies only in the case that leaf spring 52 is not ofinsulating material but is of a material like spring steel which merelyhas a higher resistance than bimetal element l8. This will, of course,have the effect of limiting the current just prior to separation of thebreaker contacts. The circuit breaker may then be manually closed bymoving operating handle 42 to the left, as viewed in Fig. 1, to moveside legs 20 of the bimetal element below the center support of centralleg 22, whereupon the element will operate with a snap action to movethe free end thereof to the closed circuit position shown in Fig. 1.

With the breaker in the closed circuit position. it will operate toautomatically open the circuit in response to the passage of currentsabove a predetermined value therethrough by the heating effect caused bysuch currents. Upon heating of the bimetal element, lamination 2|thereof will expand a greater amount than lamination 19 to thereby tendto force the ends of the bimetal element upwardly, as previouslydescribed. Since one end is secured against upward movement by extensionplate 38, the free end of the birnetal element is suddenly movedupwardly with a snap action, as in a manual operation. To reclose thebreaker following an automatic circuit interrupting operation thereof,it is necessary to actuate handle 42 to the left, as previouslydescribed.

An important feature of the breaker illustrated in Figs. 1 to 3 of thedrawing resides in the particular construction thereof and assembly ofthe parts. Thus, the breaker may be readily dissembled by merelyremoving cover 8 and threaded pin 68. This will permit extension plate38 to be lifted from wedge-shaped member l6 and the entire unitcomprising supporting plate 38 and bimetal element l8 may then be movedto the ht. as viewed in Figs. 1 and 2, to move cars 32 on the supportingplate along grooves 36 in the casing until they are in alignment withgroove 34, whereupon this unit may be then lifted out of the casing. Theonly other parts mounted in the casing are terminals 18 and I2, so thatthe construction disclosed herein provides a single mounting unitcomprising a bimetal element and supporting plate therefor which alsocarries a stop screw 56 for the bimetal element, which unit i readilyremovable as described above. To insert a unit in the casing, it ismerely necessary to line up ears 32 on supporting plate 30 with grooves34 in the casing walls, and then insert the unit into the casing until vthe intersection of grooves 36 is reached, whereupon the entire unit ismoved to the left until the transverse groove on extension plate 38receives the top edge of wedge-shaped member I6,

whereupon pin 40 may be inserted in position to hold the unit inoperative position within the cas ng. The top edge of wedge-shapedmember I6 being received in a. transverse groove provided in the lowersurface of extension plate 38,

will prevent longitudinal movement of the breaker unit within thecasing, and cars 32 on supporting plate 30 being received inlongitudinally extending grooves 36 will prevent movement of the unitlaterally into and out of the casing.

In the embodiment of the invention shown in Figs. 4 and of the drawings,the bottom-wall of the casing is provided with a threa'ded sleeve 60 forreceiving a supporting stud 62 for central leg 22 of the bimetalelement, and this leg, together with leaf spring 52, is secured to stud62 by a screw 64 threadedly engaging a threaded socket in the top ofstud 62. The construction includes many parts already described inconnection with the embodiment of the invention shown in Figs. 1, 2, and3, and hence the description of these parts will not be repeated. Itwill be noted that terminal l2 in this instance is provided with ablock-like head 66.

on which one end of bimetal element I8 is directly secured as byscrews68. An actuating member 69 is riveted or otherwise secured to thebimetal elementbetween block 66 and supporting stud 62 at one end oflegs 28 and 22, and this actuating member is provided with a slot at theupper end thereof for receiving an actuating pin 12 secured to anoperating member 14. The operating member 14 is pivotally mounted on apin 16 extending transversely of the casing and rotatably mounted insidewalls 6 thereof; Operating member '14 projects out through anOpening I8 provided in the adjacent end wall 4 of the casing for manualoperation of the breaker. The adjustable stop screw 56 is separatelysupported in this instance' from the casing, as for example, by a block88f having the ends thereof seated in slots in posite side walls 6.

In the operation of the embodiment of the invention shown in Figs. 4 and5 of the drawings,

the breaker may be opened from the closed cir-.

cuit position shown in Fig. 4 by moving operating handle 14 downwardly.This causes movement of actuating member 68 to the right, as

iber

cf the breaker casing and terminates in a rounded and adapted to bereceived in a rounded notch viewed in Fig. 4, because of the action ofpin 12 in slot Ill, and this will cause upward bending of the portion ofbimetal element l8 to which actuating member 69 is secured to move sidelegs 20 of the bimetal element above the center support of central leg22 and cause the same to snap to open circuit position, as in theembodiment of the invention already described. The circuit breaker maybe closed by moving operating handle 14 upwardly, or in acounter-clockwise direction. Automatic operation of the breaker to opencircuit position will take place in exactly the sam manner as in theembodiment of the invention shown in Figs. 1 to 3, and, therefore. willnot be repeated.

Since in this embodiment of the invention, the bimetal. element is notpivotally mounted on ter-- minal I 2, it may be a little harder toactuate manually, and that is one reason for utilizing aforce-multiplying means, such as operating member 14. However, becauseof the fixed nature of the mounting of bimetal element I8 on terminall2, a better electrical connection is obtained and all of thesnap-acting movement results in movement of the free end of the bimetalelement carrying bridging contact 58 so that a greater throw of thecontact is available. This will be accompanied by somewhat greater speedof contact movement, and, consequently, more positive action thereof. Itwill be noted that the method of assembly of the parts of the breakershown, in Figs. 4 and 5 is diiferent from that of the embodiment of theinvention shown in Figs. 1 to 3 in that the bimetal element is supportedon stud 62 which is carried by bottom wall 2 of the casing. Furthermore,stop screw 56 iscarried by a separate element 88, and the bimetalelement is relatively rigidly secured within the casing, so that, it isnecessary to as stud 62, to remove the bimetal element. Furthermore,operating member 14 is mounted on the casing and can be removed only byremoval of pivot pin 16.

In Fig. 6, still another embodiment of the invention is disclosed, buthere too, many of the parts used are like the parts used in thepreviously described embodiments of the invention, so

that like reference numerals will be used to designate these parts, anda complete description of such parts will not be given in order to avoidrepetition. In this embodiment of the invention, bimetal element I8 isprovided at one end thereof with a substantially V-shaped bent portion8| adapted to be positioned in a groove provided in the head of terminalI2 extending substantially transversely of. the breaker casing. Thisbent portion 8| is maintained inthe groove by pin 48 to prevent relativelongitudinal movement of the unit comprising bimetal element l8,supporting plate 38, and parts mounted thereon. An actuating member 82is secured to the bimetal element adjacent pin 40, between this pin andthe center support of central leg 22. Actuating mem- 82 extends upwardlyand towards the center 84, provided in an operating member 86 pivotallymounted in the casing. Operating member 86 A preferably is secured on anoperating pivot shaft 88 which is received in notches 98 provided in theupper edges of opposite casing sidewalls 6, and has one end extendedoutside the casing to mount a handle 82. In this embodiment of theinvention, but a single contact button 94 is pro-' vided on the free endof bimetal element l8 in remove screw 68, as well place of thedouble-break bridging contact structure 50 of the previously describedembodiments of the invention, 1

The operation of this embodiment is much like that of the constructionspreviously described. In this construction, counter-clockwise movementof handle 92 causes clockwise movement of actuating member 82 to moveside legs 10 oi. the bimetal element above the center support of centralleg 22 from the position shown in Fig. 6, to cause the bimetal elementto snap to an open circuit position. Movement 01 the operating nandle 92in a clockwise direction will obviously cause closing of the breakercontacts with a snap action. When the breaker is in closed circuitposition, it may also automatically operate to open the circuit in thesame manner as the previously described embodiments of the invention bythermal action of bimetal element is.

The method of assembly of the embodiment of the invention shown in Fig.6 is much like that of the device shown in Figs. 3 to 3, in that thebimetal element is and supporting plate 30 form a unit which isremovable from the casing merely by removing pin 40 and moving this unitalong grooves 36 and 34, as in the embodiment oi the invention shown inFigs. 1, 2 and 3. It will be noted that operating member 38 ismaintained in notches 90 by cover 8 so that this may be easily liftedout of place merely by removal of the cover.

It is believed apparent from the foregoing that there is disclosedherein a circuit breaker of the type utilizing a snap acting blmetalelement for actuating the breaker contacts wherein a novel arrangementoi supporting means for such a bimetal element is disclosed forobtaining movement of one end of the bimetal element to actuate thebreaker contacts. Furthermore, a novel arrangement of actuating meansand bimetal element of the type described is disclosed, as well as anovel double break contact, and novel methods of assembling the parts inan enclosing casi g.

Having described preferred embodiments of the invention in accordancewith the patent statutes, it should be understood that the inventionshould not be limited to the particular constructions described inasmuchas it will be obvious, particularly to persons skilled in the art, thatmany changes and modifications may be made in these particularconstructions without departing from the broad spirit and scope of theinvention. Therefore, it is desired that the invention be interpreted asbroadly as possible, and that it be limited only as required by theprior art.

I claim as my invention:

1. In a circuit breaker, a himetal element which is elongated in form,said element having a pair of spaced, longitudinally extending slotstherein defining opposite side legs and a central leg, the effectivelength of said central leg being greater than the effective length ofsaid side legs, whereby said central leg is longitudinally compressedand normally assumes a bowed form and said side legs are under tension,means supporting an intermediate portion of said central leg tral leg tocause said central leg to reverse its curvature and move said contactmeans into and out of engagement with said contact with a snap action. v

2. In a circuit breaker, a resilient bimetal element which is elongatedin form, said element having an intermediate portion which normallyassumes a bowed form, means adjustably supporting said portion of saidelement, means movably supporting one end of said element, contact meanscarried by the other end of said element, a relatively stationarycontact cooperating therewith, and manually operable means secured tosaid element adjacent said one end thereof for moving at least a portionof said element in opposite directions sufllclent-ly to cause saidcurved portion to reverse its curvature and move said contact means intoand out of engagement with said contact with a snap action.

3. In a circuit breaker, a resilient b metal element which is elongatedin form, said element having an intermediate portion which normallyassumes a bowed form, means supporting said portion of said element,means movably supporting one end of said clement, contact means carriedby the other end of said element, a relatively stationary contactcooperating therewith, and manually operable means rigidly secured tosaid element adjacent said one end thereof for moving at least a portionof said element in opposite directions an amount sufllcient to causesaid curved portion to reverse its curvature and move said contact meansinto and out of engagement with said contact with a snap action.

4. In a circuit breaker, a resilient bimetal element which is elongatedin form, said element having an intermediate portion which normallyassumes a bowed form, means supporting said portion of said element,means movably supporting one end of said element, contact means carriedby the other end of said element, a relatively stationary contactcooperating therewith, actuating means rigidly secured to said one endoi! said element for moving at least a porlton of said element inopposite directions an amount suilicient to cause said curved portion toreverse its curvature and move said contact means into and out ofengagement with said contact with a snap action, and a pivotally mountedactuating handle manually operable for actuating said actuating means.

5. In a circuit breaker, a bimetal element which is elongated in form,said element having a pair of spaced, longitudinally extending slotstherein defining opposite side legs and a central leg, the effectivelength of said central leg being greater than the effective length ofsaid side legs, whereby said central leg is longitudinally compressedand normally assumes a bowed form and said side at a predeterminedposition, means movably supporting one end of said element, contactmeans mounted on the other end of said element, a-relatively stationarycontact cooperating with said contact means, and manually operable meanssecured to said one end of said element for moving said side legs inopposite directions to opposite sides of the support of said cenlegs areunder tension, means supporting an intermediate portion of said centralleg, means pivotally supporting one end of said element about an axisextending substantially transversely of said element, contact meansmounted on the other end of said element, a relatively stationarycontact cooperating therewith, and manually operable means secured tosaid element at a point intermediate said supporting means for movingsaid side legs to opposite sides of the support of said central leg tocause said central leg to reverse its curvature and move said contactmeans into and out of engagement with said contact with a snap action.

6. In a circuit breaker, a blmetal element which is elongated in form,said element having an inone end or said element, meansmovablysupporting the outer end of said' extension member, con tact meanscarried by the other end of said ele-' ment, a relatively stationarycontact cooperating therewith, and manually operable means secured tosaid element adjacent said one end thereof for moving at least a portionof said element in opposite directions an amount sufllcient to causesaid curved portion to reverse its curvature and move said contact meansinto and out of engagement with said contact with a snap action.

7. In a circuit breaker, a bimetal element said relatively stationarycontact member, a bridging contact, relatively high resistance meansresiliently supporting said bridging contact from i said movable contactmember to normally position said bridging contact intermediate andspaced from said contact members in the open a circuit position of saidinterrupter, whereby upon which is elongated in form, said elementhaving an intermediate portion which normally assumes a bowed form,means supporting said portion of said element, an extension membersecured to one end of said element, means movably supporting the outerend of said extension member, contact means carried by the other end ofsaid element, a relatively stationary contact cooperating therewith, andmanually operable means secured to said extension member for moving atleast a portion of said element in opposite directions an amount tocause said curved portion to reverse its curvature and move said contactmeans into and out of engagement with said contact with a snap action.

8. In a circuit breaker, a blad element which is elongated in form, saidelement having an intermediate portion which normally assumes a bowedform, means supporting said portion of said element, means movablysupporting one end of said element, contact means carried by the otherend of said element, a relatively stationary contact cooperatingtherewith, manually operable means secured to said one end of saidelement for moving at least a portion of said element in oppositedirections an amount sufllcient movement of said movable contact membertoward said relatively stationary contact member said bridging contactwill engage between both of said contact members to shunt out saidresistance means, and upon separation 01' said contact members saidresistance means is introduced in series in the circuit before an arc isdrawn.

v 11. In a. circuit breaker, a bimetal element which is elongated inform, said element having a pair of spaced, longitudinally extendinslots therein defining opposite side legs and a central leg, theeffective length of said central leg being greater than the efiecti-velength of said side legs, whereby said central leg is longitudinallycompressed and normally assumes a bowed form and said side legs areunder tension, means sup porting an intermediate portion of said centralleg, means movably supporting one end of said element, contact meanscarried by the other end of said element, a relatively stationarycontact to cause said intermediate portion to reverse its curvature andmove said contact means into and out of engagement with said contactwith a snap action, said contact means including a bridging contact,resistance means resiliently supporting said bridging contact on saidelement at sai other end thereof, said bridging contact normal" lypositioned intermediate said element and stationary contact by saidresistance means to provides. double break in the circuit when thebreaker is in open position, and whereby upon movement of said elementto closed circuit position said bridging element is moved intoengagement with said relatively stationary contact and is directlyengaged by said element.

9.- In a circuit interrupter, contact members relatively movable towardsand away from each other, a bridging contact, relatively high resistancemeans resiliently supporting said bridging contact from one of saidcontact members to normally position said bridging contact intermediateand spaced from said contact members in the open circuit position ofsaid interrupter, whereby upon movement of said contact members towardseach other said bridging contact will engage between both of saidcontact members to shunt out said resistance means, and upon separationof said contact members said resistance means is introduced in series inthe circuit before an arc is drawn. 7

10. In a circuit interrupter, a relatively stationary contact member. acontact member mounted for movement toward and away from secured to saidone end of said element for mov ing said side legs to opposite sides ofthe support of said central leg to cause said central leg to reverse itscurvature and move said contact means into and out of engagement withsaid contact with a snap action, said contact means including a bridgingcontact, a leaf spring having a relatively high resistance supportingsaid bridging contact from said supporting means for the central leg ofsaid element so that said bridging contact is positioned adjacent saidother end of said element and normally intermediate said element andstationary contact to provide a double break in the circuit when thebreaker is in open position, and whereby upon movement of said elementto closed circuit position said bridging element is moved'intoengagement with said relatively stationary contact and isdirectlyengaged by said element.

terminals, operating means for said movable contact means, a unitarysupport for at least a.

portion of said means, said support having oppositely projecting tonguesfor reception in said grooves whereby said support may be insertedthrough the opening of said casing with said tongues received in saidfirst mentioned grooves and then moved laterally when said tongues arealigned with said intersecting grooves, and means for releasablysecuring said support against movement of said tongues out of saidintersecting grooves for releasably securing said support and meanscarried thereby in said casing.

13. In a circuit breaker, a casing having an opening, terminals onsaid-casing having portions extending to the interior of said casing,

walls of said casing at opposite sides said opening provided withsubstantially parallel grooves extending from the opening toward theopposite wall of said casing, said opposed walls also havingsubstantially parallel grooves intersecting said first mentioned groovesat an angle, movable contact means for bridging said pormounted in saidcasing for preventing escape of said projection from said recess meansfor releasably securing said support and means carrie,. thereby for saidcaslmz.

14. In a circuit breaker, a casing having an opening, terminals on saidcasing having portions ending to the interior of said casing, walls ofsaid casing at opposite sides of said opening provided withsubstantially parallel grooves extending from the opening toward, theopposite wall of said casing, said opposed walls also havingsubstantially parallel grooves intersecting said first mentioned groovesat an angle, movable contact means for bridging said portions of saidterminals including a bimetal element, a unitary assembly of saidbimetal element and a support therefor, said support having oppositelyprojecting tongues for reception in said grooves whereby said supportmay be inserted through the opening of said casing-with said tonguesreceived in said first mentioned grooves and then moved laterally whensaid tongues are aligned with said intersecting grooves, and means forreleasably securing said support against movement of said tongues out ofsaid intersecting grooves for releasably securing said support and meanscarried thereby in said casing.

15. In a circuit breaker, a casing having an opening, terminals on saidcasing having por tlons extending to the interior of said casing,

aligned with said intersecting means for releasably securing saidreleasably securing said support against movement of said tongues out orsaid intersectlnz grooves for releasably securing said support and meanscarried thereby in said casing.

16. In a circuit breaker, a casing, a blmetal element which is elongatedin form, said element having a pair of spaced, longitudinally extendingslots therein defining opposite side legs and a central leg, theeflective length or said central leg being greater than-the eflectivelength cl said side legs, whereby said central leg is longitudlnaliycompressed and normally assumes a bowed form and said side legs areunder tension, means supporting an intermediate portion of said centralleg on one wall or said casing, spaced terminals on said one wall ofsaid casing, means supporting one end or said element on one 01 saidterminals, contact means carried by the other end of said element formovement into and out of engagement with the other or said terminals,and manually operable means secured to said one end of said element formoving said side legs to opposite sides of the support of said centralleg to cause said central leg to reverse its curvature and move saidcontact means into and out of engagement with said contact with a snapaction.

wells of said casing at opposite sides of said opening provided withsubstantially parallel grooves extending from the opening toward theopposite wall of said casing, said opposed walls having substantiallyparallel grooves intersect ing said first mentioned grooves at an angle}movable contact means for bridging said portions of said terminalsincluding a bimetal element which is elongated in form, said elementhaving a pair of spaced, longitudinally extending slots therein definingopposite side legs and a central leg, the eflective length of saidcentral leg being greater than the effective length of said side legswhereby said central leg is longitudinally compressed and normallyassumes a bowed form and said side legs are under tension, meanssupporting an intermediate portion of said central leg,

said supporting means having oppositely projecting tongues for receptionin said grooves whereby said support may be inserted through the openingof said casing with said tongues received in said first mentionedgrooves and then moved laterally when said tongues are aligned with saidintersecting grooves, and means for 17. In a circuit breaker, a casing,a bimetal element which is elongated in form, said element having apairof spaced, longitudinally extending slots therein defining opposite sidelegs and a central leg, the eflectlve length of said central leg beinggreater than the effective length of said side legs, whereby saidcentral leg is longitudinally compressed and normally assumes a bowedform and said side legs are under tension, means supporting anintermediate portion of said central leg on one wall of said casing,spaced terminals on said one wall of said casing, means supporting oneend of said element on one 0! said terminals, contact means carried bythe other end of said element for movement into and out of engagementwith the other of said terminals, manually operable means secured tosaid one end of said element for moving said side legs to opposite sidesof the support of said central leg to cause said central leg to reverseits curvature and move said contact means into and out of engagementwith said contact with a snap action, and stop means supported fromanother wall of said casing for limiting movement of said other end ofsaid element away Irom'said other terminal.

18. In a circuit breaker, a casing having an opening terminal on saidcasing having portions extending to the interior of said casing, wallsof said casing opposite sides of said opening provided withsubstantially parallel grooves extending from the opening toward theopposite wall of said casing, said opposed walls having substantiallyparallel grooves intersecting said first mentioned grooves at an angle,movable contact means for bridging said portions of said terminalsincluding a bimetal element which is elongated in form, said elementhaving a pair of spaced,

ongitudinally extending slots therein defining opposite side legs and acentral leg, the effective length of said central leg being greater thanthe effective length of said side legs, whereby said central leg islongitudinally compressed and normally assumes a bowed form and saidside legs are under tension, means supporting an intermediate portion ofsaid central leg, said support including stop means for limitingmovement of said element out of bridging relation with respect to saidterminals, said support having oppositely projecting tongues forreception in said.

tion, whereby said element is movable with a snap action upon reversalof said curvature, spaced supporting means for one end of said elementand said portion, respectively, contact means carried by the-other endof said element, a relatively stationary contact cooperating therewith,and manually operable means secured to said element intermediate saidsupporting means for moving at least a portion of said element to causereversal of curvature of said curved portion and movement of saidcontact means into and out of engagement with said contact.

20. In a circuit breaker, a bimetal element which is elongated in form,said element having at least one longitudinally extending slot thereindefining side legs the efiective lengths of which differ whereby atleast one of said legs normally assumes a bowed form, spaced meanssupporting an end of said element and an intermediate portion of saidbowed leg, respectively, contact means carried by the other end of saidelement, and manually operable means secured to said element betweensaid supporting means to flex said element in opposite directions anamount suificient to cause said bowed leg to reverse its curvature andmove said control means in opposite directions with a snap action. I

21. In a circuit breaker, a bimetal element which is elongated in form,said element having a pair of spaced, longitudnally extending slotstherein defining opposite side legs and a central leg, the effectivelength of at least one of said legs being greater than another legwhereby said one leg normally assumes a bowed form, spaced meanssupporting an end of said element and an intermediate portion of saidbowed leg, respectively, contact means carried by the other end of saidelement, and manually operable means secured to said element betweensaid supporting means to flex said element in opposite directions anamount suflicient to cause said bowed leg to reverse its curvature andmove said contact means in opposite directions with a snap action.

22. In a, circuit interrupter, a resilient blade element which iselongated in form, said element .being deformed in a manner such that atleast an intermediate portion thereof is normally curved in sectionwhereby said element is movable with a snap action upon a reversal ofcurvature of said intermediate portion, spaced supporting means for oneend ofsaid element and said portion, respectively, contact means carriedby the other end of said element, a relatively stationary contactcooperating therewith, and manually operable means secured to saidelement for moving at least a portion of said element in oppositedirections sufiiciently to cause reversal of curvature of said curvedporton and movement of said contact means into and out of engagementwith said contact with a snap action.

23. In a circuit interrupter, a resilient blade element which iselongated in form, said element having an intermediate portion whichnormally assumes a bowed form, means supporting said portion of saidelement, contact means carried by one end of said element, a, relativelystationary contact cooperating therewith, and manually operable meansrigidly secured to said element at a point adjacent the other endthereof for moving at least a portion of said element in oppositedirections an amount sumcient to cause said curved portion to reverseits curvature and move said contact means into and out of engagementwith said contact with a snap action.

24. In a circuit breaker, a casing having an opening, terminals on saidcasing having portions extending to the interior of said casing, wallsof said casing at opposite sides of said opening provided withsubstantially parallel grooves extending from the opening toward theopposite wall of said casing, said opposed walls also havingsubstantially parallel grooves intersecting said first mentioned groovesat an angle, movable contact means for bridging said portions of saidterminals including a bimetal element, a unitary assembly of saidbimetal element and a support therefor, said support having a, stopmember adjustably mounted thereon so as to be engageable with saidbimetal element to limit opening movement thereof, said support havingoppositely projecting tongues for reception in said grooves whereby saidsupport may be inserted through the opening of said casingwith saidtongues received in said first mentioned grooves and then movedlaterally when said tongues are aligned with said intersecting grooves,and means for releasably securing said support against movementofsaidtongues out of said intersecting grooves for releasably securingsaid support and means carried thereby in said casing.

EDWIN E. ARNOLD.

